So I lost ~19lbs, down to 359 from 350 through diet and walking alone, then I plateaued out for about two months. Not going anywhere is better than up right?

I Just started couch to 5k (9/26), about to go for week 2, day 2 when I finish the post.
But I weighed myself today and I was up to 354.4! I diligently track calories every day, and the math I have adds up to a net calorie defecate (although that's what happened when I plateaued). For example, through September 22 I have a net defecate of 6683 calories should be 1.9lbs lost.

Am I over thinking this? I feel better for the exercise and I have more energy.
Is gaining some weight when you start serious exercise a thing? Anyway, off to my jog!

Okay, I'm going to pass on commenting about the 6683 net calorie defecate. Because I really am speechless at that one.

However, I can say for sure that weight gain when you start exercising is not due to muscle building...it doesn't happen that fast, or make that much of a difference, but what may be happening in your case is that with exertion, muscles retain water. That can add to weight. It should stabilize out over time. Additionally, other factors, such as sodium intake or your monthly cycle (provided you're female) can add pounds temporarily).

Also, it is important to remember that just because you have calculated a calorie deficit doesn't mean that you will see a loss that exactly corresponds to that deficit. Several factors influence your weight at any given time, and the measurement of the calories is negligible at best. But it does yield a drop over time.

Hang with it, keep doing what you need to do, and congratulations on your results so far! We'd love it if you stuck around and shared the journey with us. Holler if we can help in any way .

__________________Cassie

And now that you don't have to be perfect, you can be good.
-John Steinbeck

Sorry I didn't see this last week. But better late than never.....
My weight can fluctuate over 5 pounds in just a few days. I know it has to do with water and waste retention. Even if I were eating at a surplus I couldn't eat 17,500 calories over in such a short time. If I am diligent about drinking lots of water the fluctuations are much less. (Strange how your body releases more water when you drink more.)

Just keep at it, consider increasing your water intake especially on days you exercise, don't worry about the speed bumps. Don't expect your weight loss to be a straight line without bumps.